|Veröffentlichungsdatum||16. Aug. 2005|
|Eingetragen||4. März 2003|
|Prioritätsdatum||4. März 2003|
|Auch veröffentlicht unter||US20040177210|
|Veröffentlichungsnummer||10379759, 379759, US 6931479 B2, US 6931479B2, US-B2-6931479, US6931479 B2, US6931479B2|
|Erfinder||Joo S. Choi|
|Ursprünglich Bevollmächtigter||Micron Technology, Inc.|
|Zitat exportieren||BiBTeX, EndNote, RefMan|
|Patentzitate (15), Referenziert von (11), Klassifizierungen (29), Juristische Ereignisse (7)|
|Externe Links: USPTO, USPTO-Zuordnung, Espacenet|
The present invention relates generally to integrated circuits, and more specifically, approaches to providing more power efficient and greater functionality semiconductor memory devices through the use of multi-functional inputs and terminals.
Semiconductor memory devices have continued to have increased memory capacity, decreased access times, and greater functionality over their predecessors. However, as a result of designing memory devices having higher capacity, higher speed, and greater functionality, current memory devices typically consume more power than their predecessors during normal operation. Additionally, the number of inputs, or correspondingly, the number of signals that need to be provided to a memory device for normal operation has increased significantly.
Although power consumption has been in the past of some concern, it has more recently become an issue of much greater significance. There are many reasons for wanting to design more power efficient memory devices. One such reason is that many applications in which current memory devices are used are for portable applications, which typically means that power is supplied by batteries, or other lightweight and fixed capacity power supplies. Generally speaking, consumers find it undesirable to replace batteries, or be forced to recharge batteries often. Consequently, memory device manufacturers have made an effort in designing more power efficient memory devices. Whatever the particular reason, the issue of the increased power consumption of current memory devices cannot be ignored.
With respect to the number of pins or inputs on a memory device, it is often undesirable to have a memory device with many pins. That is, more leads often means that more signals need to be provided. As a result, signal drivers, controllers, and circuit boards need to be more complex. Additionally, more leads also often means larger memory devices, or if not larger, then a memory device is very narrow pitch between leads. Neither one of these situations is looked upon as desirable.
Many different approaches have been taken to address the issue of increased power consumption of current memory devices. For example, one straight forward approach has been to use higher capacity batteries that can provide higher power over a greater period of time before the need for recharging or replacement. However, these higher capacity batteries are generally more expensive, and are often larger and heavier. Also, as previously discussed, consumers dislike the inconvenience of changing batteries or charging rechargeable batteries often. Moreover, the approach fails to directly address the issue of power consumption by memory devices.
Other approaches have been directed to designing more power efficient memory devices, for example, designing more sophisticated internal voltage regulators and internal power supplies so that relatively less power is consumed during operation of the memory device. These types of approaches are often desirable, since many of the different designs, which may not save a significant amount of power by themselves, can be incorporated together in a memory device such that the cumulative power savings are significant. Therefore, there is a need for additional approaches to designing efficient, lower-power consuming memory devices.
The present invention is directed to a memory device having multi-functional input terminals. The memory device has address terminals for receiving input signals and command terminals for receiving command signals. In one aspect of the invention, the memory device further includes a memory array having at least one bank of memory partitioned into a plurality of sub-banks of memory cells, the memory cells in each sub-bank arranged in rows and columns of memory cells. A first address decoder coupled to the address terminals and the memory array is included to select a row of memory to be accessed corresponding to a memory address represented by a first set of input signals applied to the address terminals, and a second address decoder coupled to a first portion of the address terminals and the memory array is also included to select a column of memory to be accessed corresponding to a memory address represented by a second set of input signals applied to the first portion of the address terminals. The second set of input signals includes less input signals than the first set of input signals. A command decoder coupled to the address terminals and the first address decoder generates internal control signals for performing a requested memory operation in response to receiving command signals, and a sub-bank control circuit coupled to a second portion of the address terminals and the command decoder, in response to sub-bank selection signals applied to the second portion of the address terminals, generates sub-bank control signals provided to the command decoder to select at least one of the sub-banks of memory cells on which the memory operation is performed.
In another aspect of the invention, a method of performing a memory operation on a memory array in a memory device having a plurality of address terminals and command terminals, and further having a memory array having at least one bank of memory cells arranged in rows and columns of memory cells is provided. Command signals are received on the command terminals indicative of a memory operation, a first set of address signals is received on the plurality of address terminals, a second set of address signals is received on a first portion of the plurality of address terminals, and sub-bank selection signals are received on a second portion of the plurality of address terminals concurrently with the second set of address signals. A portion of the bank of memory selected by the sub-bank selection signals is activated and the memory operation is performed thereon.
Certain details are set forth below to provide a sufficient understanding of the invention. However, it will be clear to one skilled in the art that the invention may be practiced without these particular details. In other instances, well-known circuits, control signals, and timing protocols have not been shown in detail in order to avoid unnecessarily obscuring the invention.
The memory device 100 includes a control logic and command decoder 134 that receives a plurality of command and clocking signals over a control bus CONT, typically from an external circuit such as a memory controller (not shown). The command signals include a chip select signal CS*, a write enable signal WE*, a column address strobe signal CAS*, and a row address strobe signal RAS*, while the clocking signals include a clock enable signal CKE* and complementary clock signals CLK, CLK*, with the “*” designating a signal as being active low. The command signals CS*, WE*, CAS*, and RAS* are driven to values corresponding to a particular command, such as a read, write, precharge, or auto-refresh command. In response to the clock signals CLK, CLK*, the command decoder 134 latches and decodes an applied command, and generates a sequence of clocking and control signals that control components 102-132 to execute the function of the applied command. The clock enable signal CKE enables clocking of the command decoder 134 by the clock signals CLK, CLK*.
The command decoder 134 latches command and address signals at positive edges of the CLK, CLK* signals (i.e., the crossing point of CLK going high and CLK* going low), while the input registers 130 and data drivers 124 transfer data into and from, respectively, the memory device 100 in response to both edges of a data strobe signal DQS and thus at double the frequency of the clock signals CLK, CLK*. This is true because the DQS signal has the same frequency as the CLK, CLK* signals. The memory device 100 is referred to as a double-data-rate device because the data words DQ being transferred to and from the device are transferred at double the rate of a conventional SDRAM, which transfers data at a rate corresponding to the frequency of the applied clock signal. The detailed operation of the control logic and command decoder 134 in generating the control and timing signals is conventional, and thus, for the sake of brevity, will not be described in more detail.
Further included in the memory device 100 is an address register 102 that receives row, column, and bank addresses over a multiplexed address bus ADDR. That is, the address bus ADDR is used for both row and column address signals. The bank address signals BA0 and BA1 are applied via a dedicated bank address bus (not shown). The addresses are typically supplied by a memory controller (not shown). As shown in
The address register 102 receives a row address and a bank address that are applied to a row address multiplexer 104 and bank control logic circuit 106, respectively. The row address multiplexer 104 applies either the row address received from the address register 102 or a refresh row address from a refresh counter 108 to a plurality of row address latch and decoders 110A-D. The bank control logic 106 activates the row address latch and decoder 110A-D corresponding to either the bank address received from the address register 102 or a refresh bank address from the refresh counter 108, and the activated row address latch and decoder latches and decodes the received row address.
In response to the decoded row address, the activated row address latch and decoder 110A-D applies various signals to a corresponding memory bank 112A-D to thereby activate a row of memory cells corresponding to the decoded row address. Each memory bank 112A-D includes a memory-cell array having a plurality of memory cells arranged in rows and columns, where the rows of memory cells extend the entire length of the memory bank 112A-D in which the rows are located. After a row of memory cells is activated, the data stored in the memory cells in the activated row are stored in sense amplifiers in the corresponding memory bank. Generally, there is one sense amplifier for each memory cell of a row, and as a result, when a row of memory cells is activated, a corresponding number of the sense amplifiers must be activated in order to store the data of the activated row of memory cells.
The row address multiplexer 104 applies the refresh row address from the refresh counter 108 to the decoders 110A-D and the bank control logic circuit 106 uses the refresh bank address from the refresh counter when the memory device 100 operates in an auto-refresh or self-refresh mode of operation in response to an auto- or self-refresh command being applied to the memory device 100, as will be appreciated by those skilled in the art.
As previously discussed, the ADDR bus is multiplexed so that a column address can applied to and latched by the memory device 100. The address register 102 applies the column address to a column address counter and latch 114 which, in turn, latches the column address and applies the latched column address to a plurality of column decoders 116A-D. The bank control logic 106 activates the column decoder 116A-D corresponding to the received bank address, and the activated column decoder decodes the applied column address. Depending on the operating mode of the memory device 100, the column address counter and latch 114 either directly applies the latched column address to the decoders 116A-D, or applies a sequence of column addresses to the decoders starting at the column address provided by the address register 102. In response to the column address from the counter and latch 114, the activated column decoder 116A-D applies decode and control signals to an I/O gating and data masking circuit 118 which, in turn, accesses memory cells corresponding to the decoded column address in the activated row of memory cells in the memory bank 112A-D being accessed.
During data read operations, data being read from the addressed memory cells is coupled through the I/O gating and data masking circuit 118 to a read latch 120. The I/O gating and data masking circuit 118 supplies N bits of data to the read latch 120, which then applies two N/2 bit words to a multiplexer 122. In the memory device 100 shown in
During data write operations, an external circuit such as a memory controller (not shown) applies N/2 bit data words DQ, the strobe signal DQS, and corresponding data masking signals DM0-X on the data bus DATA. A data receiver 128 receives each DQ word and the associated DM0-X signals, and applies these signals to input registers 130 that are clocked by the DQS signal. In response to a rising edge of the DQS signal, the input registers 130 latch a first N/2 bit DQ word and the associated DM0-X signals, and in response to a falling edge of the DQS signal the input registers latch the second N/2 bit DQ word and associated DM0-X signals. The input register 130 provides the two latched N/2 bit DQ words as an N-bit word to a write FIFO and driver 132, which clocks the applied DQ word and DM0-X signals into the write FIFO and driver in response to the DQS signal. The DQ word is clocked out of the write FIFO and driver 132 in response to the CLK signal, and is applied to the I/O gating and masking circuit 118. The I/O gating and masking circuit 118 transfers the DQ word to the addressed memory cells in the accessed bank 112A-D subject to the DM0-X signals, which may be used to selectively mask bits or groups of bits in the DQ words (i.e., in the write data) being written to the addressed memory cells.
As shown in
A memory bank 218 of the memory array 110 is also shown in greater detail in FIG. 2. The memory bank 218 includes sub-banks 220, 221, 222, and 223. The memory cells of each of the sub-banks 220-223 are arranged in row lines and column lines, as in a conventional fashion. However, each of the sub-banks 220-223 is coupled to a respective sub-bank row decoder 230, 231, 232, and 233. The respective sub-bank row decoders 230-233 are coupled to the row address decoder 206 to receive a sub-bank row decode signal from the row address decoder 206. Sense amplifiers 240 are coupled to the columns of the sub-banks 220-223 to store the data of the memory cells of an activated row of memory, as well known. The sense amplifiers 240 are coupled to the rest of the memory device as shown if FIG. 1 and operate in a conventional manner.
The embodiment of the present invention shown in
As will be explained in more detail below, selection of the sub-bank for which the portion of the row is activated is determined by the address signals A12-A14 provided to the memory device 200 while the address inputs are multiplexed to receive column addresses. By virtue of the memory device 200 not having a “square” array, some of the address terminals of the memory device 200 will not be used when providing either the row address or column address. As shown in
In conventional memory devices, the “remaining” address terminals are “don't cares” when latching the address. However, embodiments of the present invention take advantage of the remaining address terminals to provide greater flexibility and functionality. An advantage provided by the present invention is that no additional terminals need to be provided for implementing embodiments of the present invention. Providing additional terminals to a memory device is often undesirable because of the issues with spacing and size. For example, decreasing the space between leads to accommodate additional leads increases the likelihood of shorting. Adding leads to a memory device without changing lead spacing often results in a larger device package, which is undesirable in applications where small devices are required.
In an embodiment of the present invention, the address signals A12-A14 are provided with a “CAS command” preceding a row activation command. The “CAS before RAS” (CBR) timing is used in the embodiment in order to maintain access times for the memory device 200. Namely, the delay from an active command to execution of a read or write command, or tRCD. In the embodiment, following the row activation command, conventional CAS command timing can be used. A register 203 included in the command decoder 202 stores the CBR CAS command to play a role after a row activation command. Based on the address signals A12-A14, the command decoder 202 generates the sub-bank activation signals 204, which are provided to the row address decoder 206. In turn, the row address decoder 206 generates and provides a sub-bank row decode signal to the appropriate sub-bank row decoder 230-233 for activating the portion of the row line of the selected sub-bank 220-223. The sense amplifiers 240 for the selected sub-bank, or sub-banks 220-223, are activated to store the data of the memory cells, which are then provided to the rest of the memory device 200 in a conventional manner.
Operation of the memory device 200 will now be explained with reference to
With reference to
As previously discussed, the command decoder 202 receives the READ command 302 (i.e., a CAS command), and in response, latches the address signals A12-A14 as external sub-bank select signals. The command decoder 202 interprets the address signals A12-A14 and prepares to generate sub-bank activation signals 204, which will be provided to the row address decoder 206. The address signals A0-A11 are latched by the column address latch and the bank addresses are provided to the bank control logic 106.
At a time T2, an activation command (ACT) 304 is provided to the memory device 200, which initiates the memory access (i.e., read) operation requested by the READ command 302. The read operation will access the row of memory corresponding to the row address signals A0-A14 located in the memory bank selected by the B0/1 signals, and the column of memory corresponding to the column address signals A0-A11 latched by the column address latch in response to the READ command 302. At the time T2, the address register 208 latches the address signals A0-A14, and because the ACT command 304 represents a “RAS command,” the command decoder 202 interprets all of the address signals A0-A14 as identifying a row address. Further in response to the ACT command 304, the command decoder 202 generates the appropriate sub-bank activation signals 204 based on the external sub-bank select signals (i.e., address signals A12-A14 latched at the time T1). The sub-bank activation signals 204 are provided to the row address decoder 206 to activate the row of memory cells identified by the address signals A0-A14, which were latched in response to the ACT command 304 and the selected portions of the selected row identified by the address signals A12-A14, which were latched in response to the READ command 302. In addition to the sub-bank activation signals 204, the command decoder 202 generates conventional internal control signals to perform the read operation, as well known.
At a time T3, a second READ command 306 is provided to the memory device 200 to request a read operation. As previously mentioned, conventional signal timing can be used for CAS commands issued subsequent to the CBR timing described above. As previously described with respect to the time T1, in response to the READ command 306, the command decoder 202 interprets only address signals A0-A11 (CA) for identifying a column address, and interprets address signals A12-A14 as external sub-bank select signals to identify which sub-banks will have its portion of the row of memory cells activated. The row of memory identified by address signals A0-A14 at the time T2 is still activated, and consequently, the second read operation will be performed for the activated row and the column identified by the address signals A0-A11 at the time T3. The memory bank 218 is identified by the bank address signals BA0 and BA1 (B0/1).
At a time T4, data 312 read in response to the READ command 302 becomes available on data terminals DQ0-DQ3. At a time T5, data 316 read in response to the READ command 306 becomes available on the data terminals DQ0-DQ3. Also at the time T5, a write operation is requested by providing a WRITE command 308 to the memory device 200. The WRITE command 308 also represents a CAS command and uses conventional signal timing. As a result, a column of memory is identified by the address signals A0-A11 (CA) and address signals A12-A14 are interpreted as external sub-bank select signals by the command decoder 202. The currently activated row remains active, with only those portions corresponding to the sub-bank identified by A12-A14 activated for the write operation. The command decoder 202 will generate the appropriate sub-bank activation signals 204 based on the address signals A12-A14. At a time T6, data 318 to be written to the memory location identified by the row address signals A0-A14 latched at the time T2, and the column address signals A0-A11 latched at the time T5, is provided to the memory device 200.
With reference to
At a time T2, an ACT command 404, bank addresses B0 and BA1, and address signals A0-A14 are provided to the memory device to initiate the write operation for the row corresponding to the address signals A0-A14, in the memory bank 218 identified by the bank addresses BA0 and BA1, and for those portions of the row of memory cells corresponding to the sub-bank, or sub-banks, selected by the external sub-bank select signals provided to the memory device 200 as address signals A12-A14. The column for which the write operation will be performed was identified by the address signals A0-A11 latched at the time T1 with the WRITE command 402.
At a time T3, a second WRITE command 406 is provided to the memory device 200 to request a second write operation to be performed. The second write operation will be performed for the column identified by the address signals A0-A11, which are provided at the same time as the WRITE command 406. The memory bank 218 for the write operation is selected by the bank addresses BA0 and BA1 latched at the time T3. The write operation will be performed for the currently activated row since the row identified by the address signals A0-A14 latched at the time T2 was never precharged, or deactivated. Again, because the WRITE command 406 is a CAS command, the command decoder interprets the address signals A12-A14 as external sub-bank select signals, and will generate the appropriate sub-bank activation signals 204 to select the portions of the active row to be activated for the write operation.
At a time T4, data 412 to be written in response to the WRITE command 402 is provided to the memory device 200 on data terminals DQ0-DQ3. As previously discussed, the data 412 will be written to the memory location at the intersection of the row corresponding to address signals A0-A14 latched at the time T2, and the column corresponding to the address signals A0-A11 latched at the time T1. Additionally, only the portions of the row corresponding to the sub-banks 220-223 selected by the address signals A12-A14 at the time T1 are activated for the write operation. At a time T5, data 416 to be written in response to the WRITE command 406 is provided to the memory device 200 on the data terminals DQ0-DQ3. The data 416 will be written to the memory location at the intersection of the row corresponding to address signals A0-A14 latched at the time T2 and the column corresponding to the address signals A0-A11 latched at the time T3. Only the portions of the row corresponding to the sub-banks selected by the address signals A12-A14 at the time T3 are activated for the write operation.
Also at the time T5, a READ command 408 is provided to the memory device 200 to request a read operation. Along with the READ command 408, bank addresses BA0 and BA1, and address signals A0-A11 (CA) and address signals A12-A14 are provided to identify the bank and the column for which the read operation is performed, and additionally, since the READ command 408 represents a CAS command, select the portion of the active row corresponding to the sub-bank or sub-banks identified by the address signals A12-A14 to be activated for the read operation.
At a time T6, a precharge command (PRE) 410 is provided to the memory device 200 to deactivate currently active rows of memory. As with conventional memory devices, the bank addresses BA0 and BA1 are used if the currently active row is to be deactivated in only one of the memory banks 218. In one embodiment of the present invention, some of the address signals are used to specify a precharge code. For example, the address signal A10 can be used to specify whether active rows in all memory banks 218 should be deactivated, or whether an active row in a specific memory bank identified by bank addresses BA0 and BA1 should be deactivated. In another embodiment, the address signals A12-A14 are used for the purposes of partitioning the memory bank 218 during the precharge operation, and consequently, the address signals A12-A14 cannot be used to identify sub-banks 220-223 for individual precharging operations. At a time T7, data 418 is provided on the data terminals DQ0-DQ3 in response to the read operation requested by the READ command 408 at the time T5.
Although not specifically discussed, it will be appreciated that embodiments of the present invention can be used for CAS commands other than READ, WRITE, and precharge operations. For example, conventional memory devices often include an auto-precharge operation, where the precharge operation is handled without input or intervention by the user. An embodiment of the present invention can include such functionality, but with the flexibility of having auto-precharge capability for specific portions of rows of memory cells. As a result, the power consumed for auto-precharge operations can be reduced, and spread over a longer period of time to reduce the average power consumption.
More generally, embodiments of the present invention can provide greater flexibility than conventional memory devices in that “extra pins” of a memory device, which may be used only under specific conditions, or for specific commands, can also be used for other functions. Thus, the particular embodiments previously discussed with respect to selecting sub-banks of memory banks for which a portion of a row of memory is activated, is merely exemplary, and does not limit the scope of the present invention. For example, pins unused in a particular mode of operation can be used to provide additional functionality, such as, selecting a particular bank of memory to be placed into a standby mode while other memory banks remain active, or a particular precharge mode (e.g., auto-precharge) can be set for a memory bank, whereas the other memory banks remain in a normal precharge mode. Therefore, as described herein, embodiments of the present invention take advantage of pins that remain “unused” during particular operations, conditions, or modes, to provide additional functionality or flexibility to a memory device. Such modifications to embodiments of the present invention to provide the additional functionality and flexibility are well within the scope of the present invention, and those of ordinary skill in the art will obtain sufficient understanding from the description provided herein to practice the present invention.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
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